In recent years, support arm devices are used to support surgical operations at the medical front. For example, there is a proposed method in which an observation unit for observing a surgical site, such as a camera, is provided at a distal end of an arm unit of a support arm device, and a surgeon performs a surgical operation while watching an image captured by the observation unit. Alternatively, there is also a proposed method in which an operation tool, such as a forceps, is provided at the distal end of the arm unit, in order to cause the support arm device to perform a work that has been performed with human labor in the past, using the operation tool.
Here, in a support arm device including an actuator that is provided at each joint portion to be driven, the position and the orientation of the arm unit are controlled by controlling the driving state of a motor of the actuator. Thus, for example, when the supply of electric power to the actuator is cut off due to power outage or a similar reason, the motor is unable to be driven, which might result in a serious trouble, such as fall of the arm unit by its own weight. Thus, the support arm device having this drive mechanism is to stop safely when the electric power is cut off. Note that, in the following description, “support arm device” simply means a support arm device that can drive an arm unit by an actuator which is provided at at least one of joint portions of the arm unit, when there is no description particularly.
For example, in some industrial support arm devices used in a plant or the like, an actuator is provided with what is called a non-excitation operation electromagnetic brake that unlocks an output shaft of a motor when excited and locks the output shaft of the motor when demagnetized, in order to stop the arm unit in case of emergency, such as power outage (for example, Patent Literature 1). It might be possible to configure a safer medical support arm device by applying the technology used in this industrial support arm device to a medical support arm device.